1. Field of Invention
The present invention relates to a zoom lens and an image pick-up apparatus using the zoom lens as image pick-up lens, and particularly to a rear focus type zoom lens capable of realizing variable power of about 3× to 5× which is suitable for a small size image pick-up apparatus, such as a digital still camera and a home video camera, and to an image pick-up apparatus using the zoom lens.
2. Description of Related Art
In recent years, while a digital still camera and a digital video camera have been widespread for home use, further downsizing has been sought with respect to these small size image pick-up apparatuses. Consequently, with respect to an imaging lens mounted on these apparatuses, particularly with respect to a zoom lens, downsizing by reducing an entire length, a depth thereof and the like also has been sought. Furthermore, with respect to such an imaging lens, particularly for a digital still camera, in addition to downsizing, improvement in lens performance corresponding to a great number of pixels of an image pick-up device has been sought.
As a zoom lens having image forming performance corresponding to a related-art solid-state image pick-up apparatus with a great number of pixels and having a shortened entire length, like a zoom lens shown in Patent Document 1, there is known a four-group zoom lens composed by arranging a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power and a fourth lens group having positive refractive power in order from the object side. The zoom lens shown in Patent Literature 1 has a prism refracting a light path arranged in the first lens group for downsizing in an incident optical axis direction to the relevant zoom lens, for what is called a reduction in thickness.
[Patent Document 1] Japanese Patent Application Publication No. 2000-131610